Micro-nano manipulation tools, such as those constructed by micro-nano fabrication, including microelectromechanical systems (MEMS) based manipulation tools, have found a range of applications in various fields. These miniaturized tools extend the dexterity of human operators and enable physical interactions for material characterization, in-situ sample preparation and manipulation, as well as for the prototyping of novel micro and nano devices. These micro-nano tools can be applied to assemble nano-scaled structured into a device or system (e.g., NEMS).
The majority of MEMS based manipulation devices are constructed as a single piece, where the structural, actuating, and sensing components of the device are all physically interconnected. This configuration, however, has several disadvantages in the following aspects:
(1) Tool Customization
With the entire MEMS device fabricated as a single piece, any design modification would require the entire tool to be refabricated. In the case of MEMS based manipulation tools, tool tips are often customized according to a specific application. Typical changes in tool tips include size, shape, material, and surface treatments, while the rest of the device body remains unchanged. This customization process is highly inefficient.
(2) Tool Lifetime
The tool tip is the only part of a tool that makes physical contact with objects and surfaces to be manipulated. The tool tip is, therefore, subject to excessive bending, wear, and contamination during use. When damage is incurred on the tool tip, the entire manipulation tool is dicarded and replaced. The time and cost to replace and repackage a new device can be significant.
(3) Application Complications
Manipulation of sub-micrometer-sized objects with MEMS tools is often performed within a high vacuum chamber, such as inside a scanning electron microscope (SEM) or transmission electron microscope (TEM). Such settings require the operator to open the high vacuum chamber for every tool change. Frequent opening of the high vacuum chamber causes long pumping time and concerns of contamination to the vacuum chamber and the experimental setup. The air flow during venting and pumping of the vacuum chamber could also disturb pre-assembled structures.
To overcome these difficulties, a modular design approach may be desirable, in which various tool tips may be constructed separately from the tool body which contains sensors and actuators. A tool tip may then be selected and assembled to the tool body for a given task.
This modularized design concept was previously demonstrated for the construction of atomic force microscopy (AFM) scanning probe (see R. T. Rajendra Kumar, S. U. Hassan, O. Sardan Sukas, V. Eichhorn, F. Krohs, S. Fatikow, and P. Boggild, “Nanobits: customizable scanning probe tips,” Nanotechnology, vol. 20, 395703, 2009). These probe tips were microfabricated and individually assembled onto an AFM cantilever. The tool tips, however, cannot be made thinner without reducing the structural integrity, which in turn makes the assembly process difficult. The proposed method is also not transferable to the assembly of gripping tool tips onto tool body, which requires nanometer alignment accuracy between the two ends of gripping tool tips.
The assembly of compliant gripping tool tips onto a tool body using various mechanical based mating mechanisms was demonstrated in the past. This includes the use of piezo actuators to lock onto and transfer grasping motion to microgripping tool tips (see M. Week, and C. Peschke, “Equipment technology for flexible and automated micro-assembly,” Micro Microsystem Technologies, vol. 10, pp. 241-246, 2004). U.S. Pat. No. 7,461,882 also discloses a microgripper design, where the linear motion of a tool body is translated into grasping motion of modularized tool tips through unique mechanical assembly. Both proposed designs can enable the manipulation of objects of tens of micrometers or larger. The design approaches are not scalable for sub-micrometer object manipulation.
The assembly of modularized components using adhesives has also been demonstrated for constructing manipulation tools. Commercially available microtweezers were assembled through the use of permanent adhesives (see http://www.memspi.com/). Similarly, reversible bonding between the gripping tips and piezoelectric actuator tool body using thermal glue was demonstrated (see C. Clevy, A. Hubert, J. Agnus, N. Chaillet, “A micromanipulation cell including a tool changer,” J. Micromechanics and Microengineering, vol. 15, pp. S292-S301, 2005). Both of these approaches rely on manual assembly of micro parts, which is time consuming and produce inconsistent assembly results. Misalignments between the assembled gripping tips also prevent secured grasping of small objects, limiting their applications to manipulating objects tens of micrometers and above in size.
A number of patent documents exist focusing on individual aspects of micro scale assembly, which are the key enablers of creating modularized manipulation tools with changeable tips. U.S. Pat. Nos. 5,806,152, 6,398,280, 6,561,725, 6,672,795, 6,837,723, 6,923,669, 7,012,491, 7,025,619, 7,081,630, 7,240,420, 7,314,382 and 7,895,885 disclose specific structural designs that enable mating between microcomponents. Features include reversible mating, zero insertion forces, and integrated actuators. U.S. Pat. Nos. 7,018,575, 7,622,813 and 7,900,336 disclose approaches for improving alignment accuracy between microcomponents during the assembly process. U.S. Pat. Nos. 6,676,416, 6,923,669 and 7,096,568 disclose methods of establishing electrical connections between microcomponents.
The above patent documents each disclose one possible solution aiming to solve one certain aspect of the difficult problem of assembling micro-nano components. No solution exists which is capable of constructing a functional modular micro-nanomanipulation tool. What is needed is a design satisfying the following requirements: (1) quick and repeatable assembly and disassembly between tool body and tool tips; (2) consistent performance of assembled tool; (3) compatible with a wide range of tool tip designs (e.g., probes, grippers); (4) efficient transfer of mechanical forces, electrical signals, and thermal energy between tool body and tool tip; (5) assembly and disassembly to be done in-situ without disturbing the operating environment (e.g., vacuum); (6) amenability to robotic automation; (7) capability of manipulating objects from micrometers down to tens of nanometers in size.